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RE: Fwd: DIY alignment information from the MB list
I had this forwarded to me from the MB list. Some interesting conclusions.
I'd sure like to get this discussion back up in regards to quattros again.
Date: Mon, 1 Nov 1999 13:58:14 -0500
From: "Kurzenhauser, Peter (Peter)" <firstname.lastname@example.org>
Subject: [MB] Alignments, DIY vs. $20,000 shop machine
Folks, a discussion of this subject has come up recently, and since it's
been awhile since the last full-blown round, I'll paste below some previous
info that I had written and responded to, for the edification of our newer
listers (as well as those who didn't pay attention last time). Bottom line:
$20,000 alignment racks have nothing in accuracy over a knowledgable DIY job
with a string, carpenter's square, or track gauge. So, don't think you HAVE
to go to a "professional" to get the job done right. $20,000 alignment
racks permit a paid-by-the-hour technician to do the job quickly and get the
next car on the rack fast, which is why shops have them.
Not convinced? Read on... And feel free to disagree (heh, heh)--I am
certain of the accuracy of my experience over these last 25 years, but I've
put foot in mouth before.
<< Does anybody do their own wheel alignment? I see JC Whitney sells
several different tools for wheel aligning (i.e., measuring toe-in,
etc.). Wondering if these tools work well. If there are any DIY wheel
aligners out their, I would be interested in your experiences. Thanks.
Ken then answered:
"Don't even think about it. The tools they sell are barely accurate enough
your 54 Chevy pickup. If you want the smooth confident ride of a Mercedes
the man with the $20,000 alignment machine to align all four tires to spec.
Look too at the devices they sell and see if they expand onto the inside of
your rims. This leaves little marks in your wheels which will eventually
oxidize. DIY alignments are not feasible, except as noted above."
And now, for a different view (mine):
I've done and checked alignments visually and with string for most of my
life--I don't think I've actually paid for one in 10 years. My tires wear
evenly and all my cars steer straight (except for the effects of road
curvature). I also don't have to re-set the alignment very often, and I
suspect most people don't either, even though the tire stores try to sell it
to you every time you come in. Everyone who races cars sets their own
alignments, either this way or with a fancier track gauge. And don't think
that a $20,000 alignment rack is all that perfect either. One time I took
the same car to two different tire shops (and went back to the first shop a
second time) and had the alignment checked, because I couldn't correct for
tire wear, and they came up with different alignment settings, using the
same brand rack, no less! Having watched them closely, I am sure it has
more to do with the skill of the technician.
Basically, you need a FLAT floor, either a garage, a spot in a parking lot,
or other. NOTE: Flat doesn't mean "level" although level helps too, and
most areas that appear flat, aren't really. I use a carpenter's square to
check the camber of the wheels, putting one edge on the floor and measuring
the distance to the top rim edge and bottom rim edge, then convert that to
angle (or just jot it down for comparison to the other side). Then I do the
other side. THEN, I roll the car forward 1/2 turn of the wheels and do the
same thing again, and then I average the two sets of readings--you must do
this to correct for the fact that most wheels are not perfectly straight or
perpedicular to the axis.
I check toe-in by sighting down the front wheels with the front wheels
straight ahead, to the rear wheels and see how far outside of the rear
wheels the sight-line falls (also twice at 1/2 turn interval), correct the
number for any difference in front/rear track width, and convert that to
angle or other spec. I don't check Caster, SAI or other esoterica. If the
basic measurements are okay, the other stuff won't likely have changed
either (and if the caster changes, for example, on most cars that means you
hit something and bent suspension parts--you need a trip the front end
specialists then). Same thing for the rear wheels, only sight forward to
This sounds complicated, but after you've done it a couple times, it only
takes 5 minutes or so. Finally, over time, if I find that I'm getting an
unusual wear pattern on the tires, I'll use the indications from the wear
pattern to fine-tune the alignment settings. I also vary the adjustments to
suit my taste in handling for a particular car.
Finally, for a full discussion of suspension alignments, get the book "How
to make your car handle" by Fred Pugh (Puhn?), published by HP Books
(available at many auto parts stores, and practically every speed shop).
Then I later wrote the following:
Ken, others: I wrote the part yesterday about using a flat surface to do
the alignment (and emphasized FLAT in caps). There are two places I do
this: (1) in my garage, where I have used some concrete levelling compund
and long straight edge to trowel it flat and smooth, and (2) at racetracks,
where there are concrete pads that are flat AND level, and were put there
for racers to do alignments and weight balancing the corners of the car (no,
that doesn't involve putting weights on the bumpers!).
You can get reasonable accuracy this way. For example, on a 15" wheel, 1
degree of camber is a difference of about 1/4" between the top rim and
bottom rim, or 1/4 degree is 1/16." I do not believe the techs who run
alignment machines get to 1/4 degree the vast majority of the time. I'll
grant that measuring caster angle this way is tough, but I'll also suggest
that caster (and camber) don't come out of adjustment very often, and then
for two reasons (1) something got bent in a hard curb or pothole hit, and
(2) bushings or other parts are worn out. In either of those cases, I would
not argue with taking the car to a dealer or good shop to get the whole job
done, because, as has been pointed out on the list before, it's difficult to
do those jobs safely and easily at home without spring compressors, a press,
and other special tools.
Most of our cars now have McPherson strut-type front suspensions, which are
quite resistant to changes in caster and camber (because of the long arm of
the strut to the top of the fender area and the stiffness of the strut
assembly, and aren't very sensitive to small variations in those
measurements anyway (my experience again). In fact, I'll bet anyone that
they can't tell the difference 2 degrees of caster has
on handling, if the measurements are within 1/2 degree of each other on
opposite sides, and the effect of camber is pretty mininmal if you're in the
ballpark and the same side-to-side (okay, you guys that autocross with
40-series tires might be able to detect 1/2 degree of camber change, but
anyone with normal street tires won't). As for wear patterns that tend to
take life off the tire, caster has basically zero effect, camber, as long as
it isn't way out,
doesn't either, but toe is a dominant influence. This makes sense when you
reflect on it, as the tires are either tending to scuff towards each other
or away from each other when the car is rolling down the road.
Almost all cars specify some static toe-in (there are some exceptions,
including some front-drive cars). If this causes wear, why have any?
Because for road cars, a little toe-in makes the vehicle more stable in
straight-ahead travel, especially at high speeds, but too much causes
scuffing and "feathering" wear on the tread blocks. Also, when the car is
in motion down the road, the forces on the tires tend to spread them apart a
little (especially under braking), so some initial toe-in helps compensate
for this effect. However, some types of racers frequently set the front ends
with toe-out, because they are willing to sacrifice some stability for
quicker turning response. This is most popular in low-speed racing, such as
autocrossing or dirt track racing.
I'll leave the rear suspension settings out of the discussion, except to
note that the toe settings are different, due to the drive forces on the
wheels (for rear-drive cars) and frequently specify a small amount of
toe-out (get a book on it for more info).
Anyway, to cut this long story short, you can easily check camber and toe
without a $20,000 alignment rack, and most importantly, you can quickly
compare one side to the other to see if further checking is warranted. If
the car drives straight, handles fine, camber and toe look the same on both
sides, and doesn't have unusual wear patterns on the old tires, DON'T let
the tire guys mess with it--that is a good alignment by definition, and
they're only apt to make it worse.
Pete K, -